1. Field of the Invention
This invention generally relates to a facsimile machine, and, in particular, to a facsimile machine suitable for use as being connected to a private automatic branch exchange (PABX).
2. Description of the Prior Art
A facsimile machine capable of carrying out an automatic call operation simply by inputting of a destination telephone number and depression of a start button is well known in the art. The facsimile machine of this type, typically, includes an automatic answering net control unit (hereinafter, also referred to as AA-NCU) and a control circuit, such as a central processing unit or simply CPU. Under the control of this control circuit, NCU handles various operations, such as call placement, detection of receipt of a call from a source station, and transmission of image information.
It is often desired that the facsimile machine of this type is connected to an extension of a private automatic branch exchange (hereinafter, also referred to as PABX) and information is transmitted to an outside line through PABX from the facsimile machine connected to an extension thereof. In this case, in a manner similar to the case of calling an outside line from a common extension telephone, it is necessary for the control circuit of the facsimile machine to control AA-NCU so as to advise PABX of the fact that the call is for an outside line prior to transmission of a telephone number.
As shown in FIGS. 4a through 4c, in a structure in which a pair of lines L1 and L2, constituting an extension of PABX 1, is connected to an AA-NCU 2 of a facsimile machine and also to a telephone, when a call to an outside line is to be designated by AA-NCU 2 to PABX 1, there are three outside line access methods depending on the kind of the PABX 1 used. FIG. 4a shows the first access method, in which a relay switch S1 is switched from the telephone to the facsimile machine, thereby establishing a connection to PABX 1, and, then, a particular dial number, such as "0", is transmitted by a dial pulse generating circuit DP to PABX 1, so that PABX 1 will recognize this call to be intended for an outside line, thereby connecting the facsimile machine to an outside line. This access method is also referred to as a number type. The second access method is shown in FIG. 4b, and, as shown, an additional relay S2 is provided in series with one of the pair of lines L1 and L2 (L2 in the illustrated case) within AA-NCU 2. This method is also referred to as a flash type. This relay S2 is normally closed; however, when a call is to be placed to an outside line, as shown in FIG. 4b, after switching the relay switch S1 similarly as described above, the relay S2 is set open for a predetermined time period. Because of this, PABX 1 recognizes this call to be intended to an outside line, and, thus, establishes a connection to an outside line. FIG. 4c shows the third access method, in which AA-NCU 2 of the facsimile machine is connected to PABX 1 through a line G as well as the pair of lines L1 and L2 and the line G is connected to one of the lines L1 and L2 (L2 in the illustrated case) through a relay S3 in the interior of AA-NCU 2. This third method is also referred to as a ground type. The relay switch S3 is normally open; however, when a call to an outside line is requested, the relay switch S3 is closed for a predetermined time period after switching the relay switch S1 similarly as described above. From this, PABX 1 recognizes this call to be intended for an outside line and thus establishes a connection to an outside line.
As described above, since there are three types of outside line access method, when calling an outside line from a facsimile machine connected to an extension, the operator must supply the information regarding the outside line access method of the PABX to which the facsimile machine is connected at the time of inputting the telephone number of a destination station. For example, the access method of the PABX to which the facsimile machine is connected is of the number type, a particular number, such as "0", is input prior to the telephone number. If the PABX is of the flash type, "*" must be input prior to the telephone number; whereas, if the PABX is of the ground type, "#" must be input prior to the telephone number. Depending on which of "0", "*" and "#" has been input prior to the telephone number, the control circuit of the facsimile machine determines the outside line access type of the PABX to which it is connected, thereby carrying out a suitable operation to establish a connection to an outside line. However, this is inconvenient for the operation because the operation is required to know the type of the PABX to which the facsimile machine is connected and to carry out an appropriate operation determined by the type of the PABX.